Lecture 5 : Animal diseases

1. WISE IAS
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FOR UPSC CSE
With Dr. Nireeksha Jain

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Dr. Nireeksha Jain

3. 1. HERD IMMUNITY
2. DISEASE – FREE ZONES
3. ZERO DISEASE CONCEPT
4. CHEMOPROPHYLAXIS
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3
LECTURE
TOPICS

4. Quotations are commonly printed as a means
of inspiration and to invoke philosophical
thoughts from the reader.
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5. UPSC PYQ’s
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1) Disease prevention & disease- free zones ? (2015)
2) What is ‘ Zero- disease concept’ and Chemoprophylaxis? (2014)

6. HERD IMMUNITY
• It can be defined as the immunity conferred on a population
as a result of the presence of immune individuals within the
population.
• It reduces the probability of a susceptible animal meeting an
infected animal , so that spread of disease is slowed down or
terminated.
• This arises when a high % of herd is protected through
vaccination against a virus or bacteria, making it difficult for a
disease to spread because there are too few susceptible
people / animals left to be infected.

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Greater the proportion of individual who are resistant, smaller
the probability that susceptible individual come in contact with
infected individual.
ADVANTAGE
 Effectively stop the spread of disease in community.
 Crucial for protecting animal who cannot be vaccinated.
 Potential for infection elimination.
 Reduce risk of infection for those whom vaccination is
contraindicated (e.g. Immunosuppress eased, younger ones
or who are too ill to receive vaccination)

8. CHALLENGES IN
CREATING HERD
IMMUNITY
▪ The more infectious a disease, the greater the population
immunity needed to ensure herd immunity. For example, For
successful control of FMD, herd immunity should be about the
level of 60%.
▪ The new coronavirus in human beings herd immunity should be
achieved when around 60% of the population becomes immune
to COVID-19.
▪ However, natural herd immunity – achieved through infection
rather than vaccination – can be challenging to induce through
unchecked infection as there would be a very high rate of
serious illness and death, with health systems overwhelmed well
beyond their surge capacity, even in high-income countries. This
is why herd immunity is generally pursued through vaccination
programmes.

9. CHALLENGES IN
CREATING HERD
IMMUNITY
▪ Even when vaccines are available, it is not always
possible to achieve herd immunity for very long.
Some viruses, such as seasonal flu, mutate
frequently, evading the body’s immune response.
So immunity doesn’t always last forever, which is
why the flu shot is necessary every single year.

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RISKS TO HERD IMMUNITY
 Mass vaccination has been highly
successful in inducing herd immunity for
many diseases, protecting those that
are unable to build up immunity, such as
livestock with immune deficiencies or
whose immune systems are being
suppressed for medical reasons.

12. DISEASE – FREE ZONES
Animal Disease-free zone means a clearly defined part of a
territory containing an animal subpopulation with a distinct
health status with respect to a specific disease for which
required surveillance, control and biosecurity measures
have been applied for the purpose of international trade.
Why in News?
In order to boost exports of value-added meat products, the
Government of India has called on stakeholders to work towards
the creation of region-specific animal disease-free zones in
the country.

13. DISEASE –
FREE
ZONES
 In order to control those trans-boundary animal
diseases, various measures are required including the
system of transparent and timing disease notification,
effective regulatory measurements, and the
strengthening of veterinary services for capacity
building in diagnosis and surveillance systems and
securing resources.
 Adoption of zoning will reduce negative economic
impacts of an outbreak compared to the situation
without the concept of zoning, and produce
substantially smaller losses to the livestock sector.

14. DISEASE – FREE ZONES
▪ A zoning approach supported by regulatory services
is an important and efficient control measure of
animal diseases that are so often affecting smooth
trade and resulting in the spread and prevalence of
diseases regionally or internationally.
▪ Foot and Mouth Disease (FMD) is selected here as
an example disease for a zoning approach, as the
disease is one of the major and important trans-
boundary animal diseases occurring in the tropics

15. ZONING APPROACH FOR ANIMAL
DISEASE CONTROL
▪ In principle, “zoning” is one of the most important processes to
establish part of a country to progressively control animal diseases
and consequent eradication, and the recognized animal disease
free zone is useful for smooth international trade in animals and
animal products, with a view to defining geographical areas of
different animal health status within its territory.
▪ The type of “free zone” is a zone where the absence of the disease
under consideration has been demonstrated by the requirements
prescribed in the international standards (World Organisation for
Animal Health; OIE). A free zone is usually recognized as a lesser
danger for an importing country.

16. BASIC REQIUREMENTS FOR THE
ZONE
a) records of regular and prompt animal disease
reporting
b) regulatory measures for the prevention and control
of both FMD and FMD virus infection as well as
contingency plans,
c) the system for preventing the entry of the virus, and
d) documentation that the country has a system of
intensive and frequent surveillance for FMD in the free
zone.

17. LEGISLATION & POLICIES
The procedures required for declaring a free zone from the
disease include the following elements:
a) a national transparent animal disease reporting system in a
regular and prompt way,
b) an effective disease surveillance system,
c) the disease should be notifiable,
d) a properly functioning veterinary organization with access to
an adequately equipped and effective laboratory for a good
surveillance system
e) the veterinary authorities to accurately specify the delineations
of the zone, to describe how the boundaries will be controlled,
and
f) regulatory measures on FMD prevention in the free zone to be
taken in the event of a disease outbreak, so on.

18. INTERNATIONAL VERIFICATION
OF FREE ZONES
They may be related to
a) programming and management of activities
including certification,
b) prevention and control of disease outbreaks
c) risk analysis, epidemiological surveillance and
zoning,
d) inspection techniques,
e) diagnostic tests,
f) border controls and import regulations, etc.

19. SURVEILLANCE & MONITORING
SYSTEMS
Surveillance and monitoring systems as the base for a zoning approach
should be supported by the science of epidemiology, and incorporate-
a) agent surveillance and/or monitoring (including clinical or pathological
examination of animals,
b) the identification of pathogens and the detection of immunological (or
other) evidences of previous exposure of animals to pathogens)
c) description of host population characteristics (including genetics, animal
demographics with age, sex, breed distribution, etc.),
d) environmental assessment (including meteorological data, vector
population distributions, etc.),
e) livestock economics, slaughterhouses and markets, and epidemiological
research (including patterns of animal movements and disease spread).

20. ZERO DISEASE CONCEPT
Absence of disease in animal population or a
flock mean zero disease.
• To estimate the losses caused by a disease
• No estimate of the potential cost of reaching zero
disease status once the disease is there.
• However, surveillance, control, biosecurity system
can help a lot in eliminating the disease.
• Biosecurity management- is a combination
of management practices designed to prevent the
introduction and transmission of diseases and
disease-causing agents into a herd. Prevention of
the entry of diseases into a herd is a key component
of a herd health management plan.

21. ZERO DISEASE CONCEPT
REPRODUCTIVE RATIO CONCEPT
The basic reproductive ratio, R0, is defined as the expected
number of secondary infections arising from a single individual
during his or her entire infectious period, in a population of
susceptibles.
Steps Reducing reproductive ratio to-
• Reducing / eliminating the shedding of the agent by infected
host.
• Reducing the duration of environmental survival of agent.
• Reducing or eliminating vehicle contamination and fomite
transmission.
• Reducing the exposure of susceptible hosts
• Increasing the resistance of susceptible hosts.
• For vector borne infections,reducing the vector population.

22. CHEMOPROPHYLAXIS
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• Chemoprophylaxis- refers to the administration of a medication for the
purpose of preventing disease or infection.
• Practice of administration of an antimicrobial agent for preventing an infection
before the clinical manifestations.
• Therapeutic or curative treatment of a sick animal or group of animals follows
the diagnosis of infection and/or clinical disease in those animals.
• Control treatment (sometimes referred to in veterinary medicine as
Metaphylaxis) is the treatment of a group of animals after the diagnosis of
infection and/or clinical disease in part of the group, with the aim of
preventing the spread of infectious disease to animals in close contact and at
considerable risk and which may already be (sub-clinically) infected or
incubating the disease.
• Preventive treatment (sometimes referred to as Prophylaxis) is the treatment
of an animal or a group of animals, before clinical signs of infectious disease,
in order to prevent the occurrence of disease or infection.

23. CHEMOPROPHYLAXIS
CLASSIFICATION
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• Disease targeted prophylaxis. endocarditis, malaria /
influenza
• Host targeted prophylaxis (H/V)
• Port exposure
Tuberculosis-
Surgical prophylaxis
(To prevent surgical site infection)

24. DISEASE CONTROL &
MANAGEMENT IN POULTRY
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Routine preventative measures form the next line of defence
against disease, after providing a clean and hygienic environment
through good poultry farming practices.
Preventative measures include-
1. vaccination
2. parasite control
3. identifying and treating sick birds
4. separating multi-age flocks
5. practising routine biosecurity procedures between flocks and
staff working with them.

25. DISEASE CONTROL &
MANAGEMENT IN POULTRY
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Vaccination
Vaccination can prevent many poultry diseases. Follow a suitable vaccination program or
only buy appropriately vaccinated stock. You can request vaccination certificates from
your supplier when purchasing chicks or pullets.
Poultry vaccinations include:
 avian encephalomyelitis
 chicken anaemia
 egg drop syndrome 76 (EDS 76)
 fowl cholera
 fowl pox
 infectious bronchitis
 infectious bursal disease
 infectious coryza
 infectious laryngotracheitis
 Marek's disease
 Newcastle disease.

26. DISEASE CONTROL &
MANAGEMENT IN POULTRY
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For breeders of poultry, when vaccinating-
1. always follow the instructions on the label, including
storage conditions
2. use disposable syringes and needles
3. discard all unused vaccines, syringes and needles in a
proper manner
4. be clean, but never use detergents or disinfectants near
vaccination equipment.
5. Do not disinfect skin before vaccinating with fowl pox
or Marek's HVT vaccine, as this will kill the vaccine
virus.

27. DISEASE CONTROL &
MANAGEMENT IN POULTRY
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Parasite control
Birds that are housed on the floor and have access to pastures and outdoor areas will
have greater exposure to internal and external parasites. For birds housed in these
conditions, it is important to have a prevention program in place and treat as required.
This helps to minimise physical stress and keep birds in good condition so they can
resist disease.
Control parasites by-
1. regularly inspecting birds for external parasites
2. spraying or dusting birds thoroughly with an approved insecticide if you can see
lice or mites - spray the shed, perches and nests thoroughly, making sure the
insecticide gets into crevices
3. cleaning sheds and rotating ranges to prevent worms
4. regularly checking faecal material for any sign of worms
5. always checking the label on worming treatments for withholding periods as
some are not suitable for production birds

28. DISEASE CONTROL &
MANAGEMENT IN POULTRY
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Remove sick birds
1. Regularly observe your birds for any signs of ill
health or problems within the flock such as feather
pecking.
2. Remove sick chickens and other poultry from the
main flock and obtain a diagnosis from a qualified
person.
3. Sick birds usually appear different to healthy birds.
You can give the correct treatment once you identify
the disease or problem. Keep ill birds quarantined
from the flock until completely recovered.
4. If medication is given, it is important to adhere to
any withholding periods.

29. DISEASE CONTROL &
MANAGEMENT IN POULTRY
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Multi-age flocks-
When introducing younger birds into a flock of older birds, there is an
increased risk of disease transfer from the older birds to the younger
birds. Older birds often build resilience to diseases and disorders that
younger birds have not been exposed to.
There may also be an increased risk of feather pecking and social
issues when introducing new birds to a flock.
It is preferable from a disease perspective to run single-aged flocks.
However if this is not possible and you are running multi-age flocks:
• keep age groups separate - have an all-in and all-out system for
each age group to allow for a complete clean and disinfection of
facilities and equipment between batches
• always start work with younger poultry and finish with the oldest.

30. THANKS!
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